This invention relates generally to concentration of data transmission, particularly in telephone subscriber systems.
In known telephone subscriber systems, the average use of each subscriber line is relatively low. Because of this fact, it has been recognized that subscribers may be serviced on a multiplexed basis, wherein the number of subscribers exceeds the number of available time slots of data transmission, the time slots being allocated on a demand basis. Since each direction of a subscriber conversation is normally used less than 50 percent of the time, a further concentration of subscribers could be handled if the available time slots are assigned only when needed for signaling or for carrying speech. This is the TASI principle used successfully for transoceanic calls. (Time Assignment Speech Interpolation).
While such assignment is helpful, there is continual need for further concentration of data transmission, without undesirable degradation of quality of the received data or information, in digital or analog (audio) form.